CN108957873B

CN108957873B - Liquid crystal display device having a plurality of pixel electrodes

Info

Publication number: CN108957873B
Application number: CN201810463981.1A
Authority: CN
Inventors: 李晙豪; 尹湘淳; 赵秀仁
Original assignee: LG Display Co Ltd
Current assignee: LG Display Co Ltd
Priority date: 2017-05-18
Filing date: 2018-05-15
Publication date: 2021-07-30
Anticipated expiration: 2038-05-15
Also published as: KR20180126756A; KR102329979B1; US10663826B2; CN108957873A; US20180335678A1

Abstract

A liquid crystal display device includes: a first substrate; a plurality of gate lines and a plurality of data lines crossing each other on the first substrate to define a plurality of pixel regions; a thin film transistor electrically connected to each gate line and each data line; a first electrode having a plate shape, contacting a drain electrode of the thin film transistor, and disposed in each pixel region; a passivation layer on the first electrode; and a second electrode on the passivation layer, wherein the second electrode has an opening corresponding to the first electrode.

Description

Liquid crystal display device having a plurality of pixel electrodes

Cross Reference to Related Applications

This application claims the benefit of korean patent application No.10-2017-0061552, filed by the korean intellectual property office at 2017, 5, 18, the entire contents of which are hereby incorporated by reference.

Technical Field

The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal display device capable of effectively improving response speed and transmittance.

Background

In general, a liquid crystal display device (LCD) is driven by using optical anisotropy and polarization characteristics of liquid crystal. Since the liquid crystal has a long and thin structure, liquid crystal molecules have an alignment direction. The alignment direction of the liquid crystal molecules can be controlled by artificially applying an electric field to the liquid crystal.

Therefore, when the alignment direction of the liquid crystal molecules is arbitrarily adjusted, the alignment of the liquid crystal molecules may be changed. Therefore, due to the optical anisotropy, light may be refracted in the alignment direction of the liquid crystal molecules, thereby displaying image information.

Currently, active matrix LCDs (hereinafter, simply referred to as LCDs), in which thin film transistors and pixel electrodes connected to the thin film transistors are arranged in a matrix form, are attracting much attention due to high resolution and excellent performance in displaying moving images.

The LCD includes a color filter substrate on which a common electrode is formed, an array substrate on which pixel electrodes are formed, and liquid crystal sandwiched between the two substrates. Since the liquid crystal is driven by an electric field induced between the common electrode and the pixel electrode, the LCD has excellent characteristics such as high transmittance and aperture ratio.

Further, recently, an in-plane switching (IPS) mode LCD has been developed in which electrodes are alternately disposed on one of upper and lower substrates and liquid crystal is disposed between the upper and lower substrates to display an image.

Generally, the IPS mode LCD displays an image by adjusting light transmittance of liquid crystal having dielectric anisotropy (Δ ∈) using an electric field. The IPS mode LCD is mainly formed by attaching a color filter substrate on which color filters are formed and an array substrate on which thin film transistors are formed with liquid crystals interposed therebetween.

Here, the array substrate includes a thin film transistor, a pixel electrode, and a common electrode formed in each pixel region, each pixel region being defined on the array substrate by intersections of gate lines and data lines.

The thin film transistor supplies a data signal from the data line to the pixel electrode in response to a gate signal from the gate line.

The pixel electrode receives a data signal from the thin film transistor so that the liquid crystal is driven, and the common electrode receives a common voltage as a reference when the liquid crystal is driven. The liquid crystal is rotated according to an electric field generated by a data signal through the pixel electrode and a common voltage of the common electrode, so that light transmittance is adjusted to realize a gray scale.

Recently, a Fringe Field Switching (FFS) mode LCD having better viewing angle characteristics than the IPS mode LCD has been proposed.

Fig. 1 is a schematic view showing a related art FFS mode LCD.

As shown in fig. 1, the FFS mode LCD10 includes gate lines 43 having a line shape in one direction, and data lines 51 having a line shape crossing the gate lines 43 to define pixel regions P.

In addition, a switching element, that is, a thin film transistor Tr is formed in the pixel region P. The thin film transistor Tr is connected to the data line 51 and the gate line 43 and includes a gate electrode (not shown), a gate insulating layer (not shown), a semiconductor layer (not shown), a source electrode 55, and a drain electrode 58.

A plate-shaped common electrode 60 and a pixel electrode 70 overlapping the plate-shaped common electrode 60 are formed in the pixel region P. The pixel electrode 70 has a plurality of stripe-shaped openings op.

In this case, the plate-shaped common electrode 60 is formed on the entire surface of the display region, but a portion of the plate-shaped common electrode 60 corresponding to one pixel region P is indicated by a dotted line.

The FFS mode LCD10 having such a configuration generates a fringe field by applying a voltage to the plate-shaped common electrode 60 and the pixel electrode 70 having a plurality of bar-shaped openings in each pixel region P.

Meanwhile, recently, in order to improve the utility of the display, high response speed of the LCD has been actively studied.

Here, the response speed (hereinafter, referred to as gtg (gray to gray)) indicates the time taken from light gray to dark gray. That is, the response speed is a value obtained by measuring the time for which the luminance changes from 10% to 90%.

For example, in the case of a Virtual Reality (VR) device, since an image is viewed with eyes close to a screen, a high response speed of an LCD becomes very important.

However, since the FFS mode LCD10 uses the electro-optical effect of a fluid (i.e., liquid crystal), the response speed is limited due to the behavior of the liquid crystal. Therefore, afterimages due to the flicker are caused. In the case of the related art FFS mode LCD10, the viewing angle characteristics are improved, but there is a limit to the improvement of the response speed.

Disclosure of Invention

Accordingly, the present invention is directed to a liquid crystal display device that substantially obviates one or more problems due to limitations and disadvantages of the related art.

An object of the present invention is to provide a liquid crystal display device capable of effectively realizing both a high response speed and an improved transmittance.

Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by the practice of the invention. These objects and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.

In order to achieve the object, the present invention provides a liquid crystal display device including: a first substrate; a plurality of gate lines and a plurality of data lines crossing each other on the first substrate to define a plurality of pixel regions; a thin film transistor electrically connected to each gate line and each data line; a first electrode having a plate shape, contacting a drain electrode of the thin film transistor, and disposed in each pixel region; a passivation layer on the first electrode; and a second electrode on the passivation layer, wherein the second electrode has an opening corresponding to the first electrode.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiments of the invention and together with the description serve to explain the principles of the embodiments of the invention.

Fig. 1 is a schematic view showing a related art Fringe Field Switching (FFS) mode liquid crystal display device (LCD).

Fig. 2 is a schematic view showing the configuration of an LCD according to a first embodiment of the present invention.

Fig. 3 is a plan view illustrating a portion of an array substrate according to a first embodiment of the present invention.

Fig. 4 is a schematic view showing the configuration of an LCD according to a second embodiment of the present invention.

Fig. 5 is a plan view illustrating a portion of an array substrate according to a second embodiment of the present invention.

Fig. 6A is a plan view illustrating a pixel region of an array substrate according to a second embodiment of the present invention.

Fig. 6B is a schematic view showing an initial alignment state of liquid crystal molecules of an LCD according to a second embodiment of the present invention.

Fig. 6C is a schematic image showing the movement of liquid crystal molecules according to the second embodiment of the present invention.

Fig. 7A and 7B are schematic views showing a modification of the LCD according to the second embodiment of the present invention.

Fig. 8A is a graph showing a comparison between a transmittance change of an LCD according to a second embodiment of the present invention and a transmittance change of a related art LCD.

Fig. 8B is a graph showing a comparison between the response speed of the LCD according to the second embodiment of the present invention and the response speed of the related art LCD.

Detailed Description

Hereinafter, an LCD according to an exemplary embodiment of the present invention will be described with reference to the accompanying drawings.

[ first embodiment ]

Fig. 2 is a schematic view showing the configuration of a liquid crystal display device (LCD) according to a first embodiment of the present invention.

As shown in fig. 2, a semiconductor layer 115 may be formed in the element region TrA in which the thin film transistor Tr is formed in each pixel region P on the first substrate 110. The gate insulating layer 118 may be formed on the entire surface of the semiconductor layer 115 and the first substrate 110. The gate electrode 112 may be formed on the gate insulating layer 118 so as to correspond to the central portion 115a of the semiconductor layer 115.

In addition, an interlayer insulating film 123 having a semiconductor contact hole 125 may be formed on the entire surface of the gate electrode 112 and the first substrate 110. The semiconductor contact holes 125 expose the highly doped source and drain regions 115b and 115c exposed to the outside of the gate electrode 112 in the semiconductor layer 115, respectively.

In the foregoing description, the thin film transistor Tr having the coplanar structure is described as an example, but the present invention is not limited thereto. For example, a thin film transistor having a bottom gate structure may be used.

A source electrode 155 and a drain electrode 158 may be formed on the interlayer insulating film 123 so as to be in contact with the source region 115b and the drain region 115c through the semiconductor contact hole 125, respectively, and be spaced apart from each other.

A first passivation layer 150 and a second passivation layer 180 may be formed on the source electrode 155 and the drain electrode 158, the first passivation layer 150 and the second passivation layer 180 having a drain contact hole 153 configured to expose the drain electrode 158.

Here, the common electrode 160 may be disposed between the first passivation layer 150 and the second passivation layer 180, and the pixel electrode 170 may be disposed on the second passivation layer 180.

Here, the pixel electrode 170 may contact the drain electrode 158 through the drain contact hole 153.

On the other hand, the first alignment layer 191 may be formed on the pixel electrode 170.

As described above, since the second passivation layer 180 is formed between the common electrode 160 and the pixel electrode 170, a structure in which a fringe field is generated when a voltage is applied can be realized.

On the other hand, a black matrix (not shown) configured to prevent light leakage may be formed on an inner surface of the second substrate 120 opposite to the first substrate 110. A color filter layer (not shown) having red, green and blue color filter patterns may be formed between the black matrices.

An overcoat layer (not shown) configured to planarize a surface of the color filter layer and protect the color filter layer may be formed on the color filter layer. The second alignment layer 192 may be formed on the coating layer.

As described above, the Fringe Field Switching (FFS) mode LCD100 is manufactured by attaching the first substrate 110 and the second substrate 120 with the liquid crystal layer 198 having the liquid crystal molecules LCM interposed therebetween.

The above-described configuration of the FFS mode LCD100 is merely an example, and the present invention is not limited thereto.

Fig. 3 shows the thin film transistor Tr of fig. 2 located at an intersection portion of the gate line GL and the data line DL intersecting each other to define the pixel region P and configured to turn on/off a voltage, the common electrode 160 having a plate shape and formed at the pixel region P, and the pixel electrode 170 having a plurality of openings.

Here, the common electrode 160 is formed on the entire surface of the display region, but a portion of the common electrode 160 corresponding to one pixel region P is indicated by a dotted line. The pixel electrode 170 is disposed over the common electrode 160. The pixel electrode 170 may be connected to the thin film transistor Tr of fig. 2 through a contact hole CH.

Here, the pixel electrode 170 may have a first opening 1op extending in a direction parallel to the data line DL at a central portion thereof.

In addition, the pixel electrode 170 may have a second opening 2op, and the second opening 2op may extend in a direction parallel to the gate line GL with respect to the first opening 1 op.

Here, the first opening 1op and the second opening 2op may have a rectangular shape.

A plurality of second openings 2op may be provided so as to be spaced apart from each other.

Here, the second openings 2op may be asymmetric with respect to the first openings 1 op. That is, the pixel electrode 170 allows the stripe electrode to be formed through the second opening 2 op. Accordingly, the pixel electrode 170 may have a shape in which the second openings 2op and the stripe electrodes are alternately formed.

In this case, the FFS mode LCD100 according to the first embodiment forms an asymmetric structure with respect to the first opening 1 op.

That is, when the second opening 2op is disposed at the left side of the first opening 1op, the stripe-shaped electrode may be disposed at the right side of the first opening 1 op. When the second opening 2op is disposed at the right side of the first opening 1op, the stripe-shaped electrode may be disposed at the left side of the first opening 1 op. Accordingly, the FFS mode LCD100 may have the following electrode structure: wherein the right and left sides are not symmetrical with respect to the first opening 1 op.

Due to the structure of the pixel electrode 170, the area where the liquid crystal molecules LCM of fig. 2 rotate in the same direction becomes smaller, so that the elastic force between the liquid crystal molecules LCM increases, thereby improving the response speed of the LCD.

As described above, the response speed of the LCD100 may be considered to be improved compared to the related art FFS mode LCD10 of fig. 1.

Since disclination occurs at the boundaries between the liquid crystal molecules LCM in the case where the rotation directions of the liquid crystal molecules LCM are different, in the electrode structure of the FFS mode LCD100 according to the first embodiment, the liquid crystal molecules LCM rotate in different directions when a voltage is applied. Thus, a plurality of disclination lines may be generated, and sufficient transmittance may not be obtained.

[ second embodiment ]

A second embodiment of the present invention relates to an LCD capable of effectively realizing both high response speed and improved transmittance. Hereinafter, a second embodiment of the present invention will be described with reference to the drawings.

Fig. 4 is a schematic view showing a configuration of an LCD according to a second embodiment of the present invention, and fig. 5 is a plan view showing a portion of an array substrate according to the second embodiment of the present invention.

As shown in fig. 4, a semiconductor layer 215 may be formed in the element region TrA in which the thin film transistor Tr is formed in each pixel region P on the first substrate 210. The gate insulating layer 218 may be formed on the entire surface of the semiconductor layer 215 and the first substrate 210. The gate electrode 212 may be formed on the gate insulating layer 218 so as to correspond to the central portion 215a of the semiconductor layer 215.

In addition, an interlayer insulating film 223 having a semiconductor contact hole 225 may be formed on the entire surface of the gate electrode 212 and the first substrate 210. The semiconductor contact holes 225 expose the highly doped source and drain

regions

215b and 215c exposed to the outside of the gate electrode 212 in the semiconductor layer 215, respectively.

Further, a source electrode 255 and a drain electrode 258 may be formed on the interlayer insulating film 223 so as to be in contact with the source region 215b and the drain region 215c through the semiconductor contact hole 225, respectively, and be spaced apart from each other.

A first passivation layer 250 may be formed on the source electrode 255 and the drain electrode 258, the first passivation layer 250 having a drain contact hole 253 configured to expose the drain electrode 258.

Here, in the LCD200 according to the second embodiment of the present invention, the first electrode 260 having a plate shape is disposed on the first passivation layer 250 and is made of a transparent conductive material such as Indium Tin Oxide (ITO) or Indium Zinc Oxide (IZO).

The first electrode 260 contacts the drain electrode 258 through a drain contact hole 253 formed in the first passivation layer 250.

That is, the first electrode 260 may be formed in each pixel region P, and each first electrode 260 may be connected to each thin film transistor Tr through the drain contact hole 253.

A second passivation layer 280 may be formed on the entire surface of the first electrode 260 and the display region, and the second passivation layer 280 may be made of, for example, silicon oxide (SiO)₂) Or silicon nitride (SiN)_x) An inorganic insulating material such as benzocyclobutene (BCB) or photo acryl (photo acryl).

In addition, the second electrode 270 is formed on the second passivation layer 280 in the entire region of the display region and is made of a transparent conductive material such as Indium Tin Oxide (ITO) or Indium Zinc Oxide (IZO).

Here, the second electrode 270 may have an opening corresponding to the first electrode 260 formed in each pixel region P. The opening formed in the second electrode 270 will be described in more detail below.

Meanwhile, the first alignment layer 291 may be formed on the second electrode 270.

As described above, since the second passivation layer 280 is formed between the first electrode 260 and the second electrode 270, a structure in which a fringe field is generated when a voltage is applied can be realized.

On the other hand, a black matrix (not shown) configured to prevent light leakage may be formed on an inner surface of the second substrate 220 opposite to the first substrate 210. A color filter layer (not shown) having red, green and blue color filter patterns may be formed between the black matrices.

An overcoat layer (not shown) configured to planarize a surface of the color filter layer and protect the color filter layer may be formed on the color filter layer. The second alignment layer 292 may be formed on the coating layer.

As described above, the FFS mode LCD200 is manufactured by attaching the first substrate 210 and the second substrate 220 with the liquid crystal layer 298 having the liquid crystal molecules LCM interposed therebetween.

In the LCD200 according to an embodiment of the present invention, the drain electrode 258 and the first electrode 260 contact each other through the drain contact hole 253. However, in another embodiment, the drain electrode 258 and the second electrode 270 may contact each other through the drain contact hole 253, the first electrode 260 may be formed on the entire surface of the display region, and the second electrode 270 may be formed for each pixel region P.

In addition, one of the first electrode 260 and the second electrode 270 may be a pixel electrode, and the other electrode may be a common electrode.

The above-described configuration of the FFS mode LCD200 is merely an example, and the present invention is not limited thereto.

Hereinafter, a case where the first electrode 260 is a pixel electrode and the second electrode 270 is a common electrode will be described as an example.

Fig. 5 shows that the gate line GL and the data line DL cross each other to define the pixel region P in which the thin film transistor Tr is configured to turn on/off a voltage at a crossing portion of the gate line GL and the data line DL, the pixel electrode 260 has a plate shape and is formed in each pixel region P, and the common electrode 270 of fig. 4 has an opening 270 a.

Here, the common electrode 270 of fig. 4 is formed on the entire surface of the display region. The opening 270a of the common electrode 270 is indicated by a solid line, and the pixel electrode 260 formed in each pixel region P is indicated by a dotted line.

The pixel electrode 260 is connected to the thin film transistor Tr through the drain contact hole 253 of fig. 4.

The thin film transistor Tr is shown in the figure as having a U-shaped channel as an example. However, the channel shape of the thin film transistor Tr may be variously modified according to the structures of the source electrode 255 and the drain electrode 258 of fig. 4.

Further, the gate electrode 212 of fig. 4 of the thin film transistor Tr is shown as being formed by a part of the gate line GL itself. However, the gate electrode 212 of fig. 4 may be formed to branch from the gate line GL into the pixel region P.

Here, in the LCD200 of fig. 4 according to the second embodiment of the present invention, the opening 270a of the common electrode 270 of fig. 4 is formed to correspond to the pixel electrode 260 formed in each pixel region P.

That is, one opening 270a of the common electrode 270 of fig. 4 may be formed in one pixel region P, and the opening 270a may have a trapezoidal shape.

Fig. 6A is a plan view illustrating a pixel region of an array substrate according to a second embodiment of the present invention. Fig. 6B is a schematic view showing an initial alignment state of liquid crystal molecules LCM of the LCD200 according to the second embodiment of the present invention. Fig. 6C is a schematic image showing the movement of the liquid crystal molecules LCM according to the second embodiment of the present invention.

As shown in fig. 6A, the common electrode 270 is disposed on the pixel electrode 260, and the common electrode 270 includes an opening 270a having a trapezoidal shape. Here, the common electrode 270 corresponding to one pixel region P is indicated by a dotted line, the opening 270a of the common electrode 270 is indicated by a solid line, and the pixel electrode 260 is indicated by a dotted line.

Here, the opening 270a having a trapezoidal shape may have a short side SS and a long side LS parallel to the gate line GL of fig. 5.

Further, the opening 270a may have a first side L1 and a second side L2 connecting the short side SS and the long side LS.

The opening 270a having a trapezoidal shape may have left-right symmetry.

Here, the length of the short side SS of the opening 270a may be 0.15 to 0.3 times the width 260s of the pixel electrode 260 formed in one pixel region P.

Here, the width 260s of the pixel electrode 260 refers to a width of the pixel electrode 260 along a short axis parallel to the gate line GL of fig. 5.

Here, the length of the long side LS of the opening 270a may be 0.7 times to 0.8 times the width 260s of the pixel electrode 260.

The short side SS of the opening 270a having the trapezoidal shape and the first side L1 or the second side L2 may form a first obtuse angle θ 1 and a second obtuse angle θ 2 equal to each other. The first obtuse angle θ 1 and the second obtuse angle θ 2 may be in a range of 91 ° to 130 °.

Here, the width 260s of the pixel electrode 260 may be in the range of 5 μm to 6 μm, but is not limited thereto.

The distance T of fig. 5 between the adjacent pixel electrodes 260 in the extending direction of the gate line GL of fig. 5 may be in the range of 2 μm to 4 μm, but is not limited thereto.

Due to the pixel electrode 260 and the opening 270a of the common electrode 270 disposed above the pixel electrode 260, a desired gray level can be expressed even by the fine rotation of the liquid crystal molecules LCM of fig. 4. That is, the rise time of the liquid crystal can be reduced.

Fig. 6B shows an initial alignment state of the liquid crystal molecules LCM of the LCD200 according to the second embodiment.

Here, fig. 6B shows the first liquid crystal molecules LCM1 disposed on the first region a1, i.e., the region of the opening 270a of the common electrode 270, and the second and third liquid crystal molecules LCM2 and LCM3 disposed on the second and third regions a2 and A3, i.e., the regions of the first and second sides L1 and L2 of the opening 270a of the common electrode 270.

That is, the first liquid crystal molecules LCM1 may be liquid crystal molecules disposed in a region where the common electrode 270 and the pixel electrode 260 do not overlap each other.

Here, the first to third liquid crystal molecules LCM1 to LCM3 may be positive liquid crystal molecules having positive dielectric anisotropy (Δ ∈). In this case, the orientation direction may be a direction parallel to the second axis Y.

In addition, the first to third liquid crystal molecules LCM1 to LCM3 may be negative-type liquid crystal molecules having negative dielectric anisotropy (Δ ∈). In this case, the orientation direction may be a direction parallel to the first axis X perpendicular to the second axis Y.

Hereinafter, the case where the first to third liquid crystal molecules LCM1 to LCM3 are negative-type liquid crystal molecules having negative dielectric anisotropy (Δ ∈) will be described as an example.

Here, the first alignment layer 291 of fig. 4 of the first substrate 210 of fig. 4 and the second alignment layer 292 of fig. 4 of the second substrate 220 of fig. 4 may have the same alignment direction.

Here, the initial alignment direction of the first to third liquid crystal molecules LCM1 to LCM3 is the same direction as the first axis X.

Fig. 6C shows the movement of the first to third liquid crystal molecules LCM1 to LCM3 when a voltage is applied to the pixel electrode 260 of fig. 4 and the common electrode 270 of fig. 4.

Here, referring to fig. 6C, when a voltage is applied to the pixel electrode 260 of fig. 4 and the common electrode 270 of fig. 4, the alignment directions of the first to third liquid crystal molecules LCM1 to LCM3 are changed according to an electric field formed between the pixel electrode 260 of fig. 4 and the common electrode 270 of fig. 4.

The first to third negative-type liquid crystal molecules LCM1 to LCM3 having negative dielectric anisotropy (Δ ∈) are aligned such that their long axes are parallel to a direction perpendicular to a direction in which an electric field is applied.

In this case, since the electric fields in the different directions are balanced, the first liquid crystal molecules LCM1 disposed on the first region a1, i.e., the region of the opening 270a of the common electrode 270, do not rotate.

That is, the long axes of the second and third liquid crystal molecules LCM2 and LCM3 disposed on the second and third regions a2 and A3 rotate perpendicular to the direction of the applied electric field, but the first liquid crystal molecules LCM1 disposed on the first region a1 do not rotate.

That is, the rotation regions, i.e., the second region a2 and the third region A3, are positioned to be symmetrical to each other with respect to the fixed region, i.e., the first region a 1.

When a voltage is applied, the second liquid crystal molecules LCM2 and the third liquid crystal molecules LCM3 on the second region a2 and the third region A3, which are symmetrical to each other only with respect to the first liquid crystal molecules LCM1 on the first region a1, rotate. Thus, when the applied voltage is removed, a restoring force to return the second and third liquid crystal molecules LCM2 and LCM3 on the second and third regions a2 and A3 to an initial alignment state may be increased by the first liquid crystal molecules LCM1 on the first region a1, thereby reducing a falling time.

Further, since the second and third liquid crystal molecules LCM2 and LCM3 on the second and third regions a2 and A3 of the second embodiment of the present invention have the same rotation direction, the occurrence of disclination lines at the interface between the liquid crystal molecules LCM may be reduced in the case where the rotation direction of the liquid crystal molecules LCM is different from that of the first embodiment, thereby effectively improving transmittance.

Fig. 7A and 7B are schematic views showing a modification of the LCD200 according to the second embodiment of the present invention.

As shown in fig. 7A, the common electrode 370 is disposed over the pixel electrode 360. The common electrode 370 has an opening 370a corresponding to the pixel electrode 360 formed in one pixel region P of fig. 5.

Here, the opening 370a may have a short side SS and a long side LS parallel to the gate line GL of fig. 5.

Further, the opening 370a may have a first side L1 and a second side L2 connecting the short side SS and the long side LS.

Here, each of the first and second sides L1 and L2 may include two sides having different obtuse angles θ 1 and θ 2.

Further, as shown in fig. 7B, the common electrode 470 is disposed above the pixel electrode 460. The common electrode 470 may have an opening 470a, and the opening 470a has a hexagonal shape and corresponds to the pixel electrode 460 formed in one pixel region P of fig. 5.

The modification is merely an example, and the opening 470a of the common electrode 470 may have various shapes, such as a polygonal shape having left-right symmetry.

Fig. 8A is a graph showing a comparison between a transmittance change of an LCD according to a second embodiment of the present invention and a transmittance change of a related art LCD. Fig. 8B is a graph showing a comparison between the response speed of the LCD according to the second embodiment of the present invention and the response speed of the related art LCD.

As shown in fig. 8A and 8B, the transmittance change of the LCD200 of fig. 4 according to the second embodiment Em2 of the present invention can be considered to be faster than that of the comparative example Com, i.e., the related art LCD10 of fig. 1.

Here, the response speed of the LCD in the normally black mode is determined to be the rise time Ton, i.e., the time when the transmittance changes from 10% to 90% due to the orientation change of the liquid crystal molecules when a potential difference is applied to the liquid crystal cell. In contrast, the response speed of the LCD in the normally white mode is determined to be the falling time Toff, i.e., the time when the transmittance is changed from 90% to 10% due to the alignment inversion of the liquid crystal molecules when the potential difference is removed.

Referring to fig. 8A, the rise time Ton is a time when the transmittance on the Y-axis of the graph changes from 0.1 to 0.9. The fall time Toff is the time for the transmittance to change from 0.9 to 0.1.

Here, the transmittance of the LCD200 of fig. 4 according to the second embodiment of the present invention may be considered to rapidly increase when a voltage is applied and rapidly decrease when the applied voltage is removed, as compared to the related art LCD10 of fig. 1.

More specifically, referring to FIG. 8B, the rise time of the LCD200 of FIG. 4 according to the second embodiment of the present invention is 65% of the rise time (Ref: 100%) of the related art LCD10 of FIG. 1, and thus the rise time of the LCD200 can be considered to be improved by 35% as compared to the related art LCD10 of FIG. 1. The falling time of the LCD200 is 46.5% of the falling time (Ref: 100%) of the related art LCD10 of fig. 1, and thus the falling time of the LCD200 can be considered to be improved by 53.5% as compared to the related art LCD10 of fig. 1.

That is, the rise time Ton and the fall time Toff of the LCD200 of fig. 4 according to the second embodiment of the present invention are significantly improved as compared to the related art LCD10 of fig. 1.

As described above, in the LCD200 according to the second embodiment of the present invention, a desired gray level can be expressed by fine rotation of liquid crystal molecules through the openings of the pixel electrode and the common electrode disposed above the pixel electrode. That is, the rise time of the liquid crystal can be reduced.

Further, when a voltage is applied, only the second liquid crystal molecules and the third liquid crystal molecules on the second region and the third region which are symmetrical to each other with respect to the first liquid crystal molecules on the first region rotate. Thus, when the applied voltage is removed, a restoring force that returns the second liquid crystal molecules and the third liquid crystal molecules on the second and third regions to the initial alignment state may be increased by the first liquid crystal molecules on the first region, thereby reducing a falling time.

Further, the disclination line may be reduced, thereby effectively improving the transmittance when compared to the first embodiment.

As described above, the LCD according to the present invention can realize a display capable of a high-speed response operation by effectively improving both the response speed and the transmittance compared to the related art FFS mode LCD10 of fig. 1. For example, an afterimage can be effectively corrected in a Virtual Reality (VR) device, and at the same time, image quality can be improved.

In the present invention, the second electrode disposed over the first electrode formed in each pixel region has an opening corresponding to the first electrode to improve the rise time and fall time of the liquid crystal, thereby simultaneously achieving high-speed response and effectively improving transmittance.

While exemplary embodiments of the present invention have been shown and described, it will be understood that modifications and variations may be made thereto by those of ordinary skill in the art without departing from the spirit and scope of the present invention set forth in the following claims.

Claims

1. A liquid crystal display device comprising:

a first substrate;

a plurality of gate lines and a plurality of data lines crossing each other on the first substrate to define a plurality of pixel regions;

a thin film transistor electrically connected to each gate line and each data line;

a pixel electrode having a plate shape, contacting a drain electrode of the thin film transistor, and disposed in each pixel region;

a passivation layer on the pixel electrode; and

a common electrode on the passivation layer,

wherein the common electrode has a single closed-loop opening corresponding to a single pixel region,

wherein the single closed-loop opening has two short sides parallel to the plurality of gate lines and two long sides extending along the plurality of data lines, and the length of the two long sides is substantially longer than the length of the two short sides to provide a first rotation region, a second rotation region, and a third rotation region for the plurality of liquid crystal molecules in the single pixel region when an electric field is applied,

wherein the first rotation region is disposed between the second rotation region and the third rotation region, and when an electric field is applied, the plurality of liquid crystal molecules disposed in the second rotation region and the third rotation region rotate in a direction perpendicular or parallel to a direction in which the electric field is applied, and the plurality of liquid crystal molecules disposed in the first rotation region do not rotate.

2. The liquid crystal display device of claim 1, wherein the single closed-loop aperture has a trapezoidal shape.

3. The liquid crystal display device according to claim 2, wherein the two short sides include a first short side and a second short side parallel to the first short side, the two long sides connect the first short side and the second short side, and

the length of the first short side is 0.15 to 0.3 times the width of the pixel electrode.

4. The liquid crystal display device according to claim 3, wherein a length of the second short side is 0.7 to 0.8 times a width of the pixel electrode.

5. The liquid crystal display device according to claim 4, wherein the obtuse angle of the trapezoidal shape is in a range of 91 ° to 130 °.

6. The liquid crystal display device according to claim 1, wherein the plurality of liquid crystal molecules are located on the common electrode.

7. The liquid crystal display device according to claim 6, further comprising a second substrate over the liquid crystal molecules.

8. The liquid crystal display device according to claim 7, wherein a first alignment layer is provided between the common electrode and the liquid crystal molecules and a second alignment layer is provided between the second substrate and the liquid crystal molecules.

9. The liquid crystal display device according to claim 8, wherein the liquid crystal molecules are positive liquid crystal molecules having positive dielectric anisotropy, and an alignment direction of each of the first alignment layer and the second alignment layer is parallel to the data line.

10. The liquid crystal display device according to claim 8, wherein the liquid crystal molecules are negative-type liquid crystal molecules having negative dielectric anisotropy, and an alignment direction of each of the first alignment layer and the second alignment layer is parallel to the gate line.

11. The liquid crystal display device according to claim 1, wherein the single closed-loop opening of the common electrode has a polygonal shape that is bilaterally symmetric.

12. The liquid crystal display device according to claim 1, wherein each of the two long sides has a bent portion.

13. The liquid crystal display device according to claim 1, wherein each of the two long sides has two sides parallel to a first direction and a second direction, respectively, and the first direction and the second direction intersect the plurality of data lines and intersect each other.